1. Field of the Disclosure
The present disclosure relates to a sprinkler with a water driven turbine that causes a sprinkler nozzle to rotate to provide coverage over a desired area. More specifically, the present disclosure relates to a sprinkler with a water driven turbine that includes at least one valve that selectively diverts fluid from the turbine to prevent over speeding when the fluid is air or a combination of air and water.
2. Related Art
Sprinkler systems in northern climates should be drained or blown-out with air to clear the water and to prevent freezing damage. In many cases the simplest installation provides only for allowing the irrigation system pipes and sprinklers to be cleared of water by blowing out the system using compressed air. This can be very damaging to sprinklers including water turbines, which are normally water powered. These systems rotate at a slower speed when water is used to drive them since water is a relatively heavy incompressible fluid and does not generate high turbine stator velocities. When air from blowing out the system drives the turbines, however, very high velocities result since air is an expandable, relatively light fluid, that expands across the turbine stator onto the turbine blades.
The high turbine shaft velocities resulting from such air driving the turbine can heat the shaft and cause it to seize to the plastic housing material. This prevents the turbine from turning and renders it unusable in the future unless care is taken to limit the system air, blow-out time and pressures. This has proven to be one of the major causes for premature failure of gear driven sprinklers in colder climates. Since these sprinklers are typically only used for part of the year, they should last much longer than in warmer climates where they are run year round.
Devices are known for controlling the rotational speed of turbine-driven sprinklers. One such device, shown in Clark U.S. Pat. No. 5,375,768, is designed to maintain constant turbine speed despite variations of inlet water pressure. The patented sprinkler relies on a throttling device to direct part of the water to the turbine rotor, and a pressure responsive valve to divert some of the water around the turbine. This design, however, cannot effectively limit rotational speed when the turbine is driven by a compressible fluid such as air, and still allow the turbine to run at a sufficiently high speed when it is driven by an incompressible fluid such as water because of the rapid expansion of the compressed air as it enters the turbine chamber.
Other turbine speed limiting mechanisms are known, but to applicant's knowledge, none are known that limit turbine over-speed by distinguishing the difference in the momentum of the turbine drive fluid when it contains air to divert a portion or all of the high velocity yet much lower momentum drive fluid around the turbine blades, thus limiting turbine available power and speed.